Field of the Invention
The present invention relates to a liquid discharge apparatus which discharges a liquid from its head, and to a method for controlling the same.
Description of the Related Art
As one of printing methods, there is an ink jet method which discharges a liquid droplet (ink droplet) from a recording head and draws an image. In recent years, an ink jet type of a liquid discharge apparatus is used in various fields, for instance, in the manufacture of semiconductor devices and the like. Here, when a foreign substance adheres on an object to be drawn (for instance, a semiconductor wafer) onto which a droplet is discharged, the foreign substance occasionally causes a defect in a product and the like.
In the ink jet type of the liquid discharge apparatus, a droplet and/or a foreign substance such as paper powder in the apparatus occasionally adhere on a discharge port surface in the vicinity of a discharge port of a recording head. When the droplet and/or the foreign substance which have adhered on the discharge port surface have been left, the left droplet and/or foreign substance are dried and occasionally stick to the discharge port surface. When the droplet and/or the foreign substance have stuck to the vicinity of the discharge port, discharge characteristics such as a quantity of the droplet to be discharged from the discharge port, a discharge direction of the droplet and a discharge speed of the droplet change, and density unevenness and streaks are occasionally formed due to the disarray of dots on the object to be drawn. In addition, this sticking substance (foreign substance) also occasionally drops onto and results in adhering on the object to be drawn.
There is a technology of sweeping (wiping) the discharge port surface with a wiper, as a technology of removing the droplet and/or the foreign substance which have adhered on the discharge port surface. However, in this technology, the discharge port surface is mechanically wiped, and accordingly wear and peeling occasionally occur on a member on the discharge port surface.
Then, Japanese Patent Application Laid-Open No. H05-077437 discloses a technology of blowing air onto the discharge port surface, and thereby blowing off and removing the droplet and/or the foreign substance which have adhered on the discharge port surface. According to this technology, no wiper needs to mechanically come in contact with the discharge port surface, and accordingly the wear and the peeling of the member on the discharge port surface do not occur, but the deposited substance which has adhered on the discharge port surface can be removed.
When the droplet and/or the foreign substance which have adhered on the discharge port surface are blown by blowing air, the blown droplet and/or foreign substance occasionally result in adhering on the discharge port surface again.
In the technology disclosed in Japanese Patent Application Laid-Open No. H05-077437, a positional relationship between an injection orifice of air and the discharge port surface is fixed, and the position on the discharge port surface to which air is blown shall be fixed. Because of this, even when the blown droplet and/or foreign substance have adhered on the discharge port surface again, air is not blown to the place, and it is difficult to blow the droplet and/or foreign substance again which have adhered again. In addition, in some places, the droplet and/or the foreign substance occasionally are not sufficiently removed even though the air is blown thereto.
For this reason, in the technology for removing the droplet and/or the foreign substance by blowing air, which is disclosed in Japanese Patent Application Laid-Open No. H05-077437, there are such problems that unevenness occurs in a region on the discharge port surface, from which the deposited substance such as the droplet and the foreign substance can be removed, and the deposited substance has a possibility of resulting in remaining in the vicinity of the discharge port.